PURPOSE OF STUDY: The objectives of this study are: (1) to monitor etoposide trough levels and determine the pharmacodynamic relationships benween etoposide concentration, tumor response, and toxicity, as well as the pharmacokinetic relationship between etoposide concentration and age; (2) to evaluate the response rate and response duration of previously treated non-Hodgkin's lymphoma IWF A-H to daily oral etoposide; (3) to assess the toxicity of oral etoposide in patients with relapsed NHL.